This Article reports the findings of the largest and most comprehensive study to date of the role qualified immunity plays in constitutional litigation. Qualified immunity shields government officials from constitutional claims for money damages so long as the officials did not violate clearly established law. The Supreme Court has described the doctrine as incredibly strong—protecting “all but the plainly incompetent or those who knowingly violate the law.” Legal scholars and commentators describe qualified immunity in equally stark terms, often criticizing the doctrine for closing the courthouse doors to plaintiffs whose rights have been violated. The Court has repeatedly explained that qualified immunity must be as powerful as it is to protect government officials from burdens associated with participating in discovery and trial. Yet the Supreme Court has relied on no empirical evidence to support its assertion that qualified immunity doctrine shields government officials from these assumed burdens. This Article is the first to test this foundational assumption underlying the Supreme Court’s qualified immunity decisions. I reviewed the dockets of 1,183 Section 1983 cases filed against state and local law enforcement defendants in five federal court districts over a two-year period and measured the frequency with which qualified immunity motions were brought by defendants, granted by courts, and dispositive before discovery and trial. I found that qualified immunity rarely served its intended role as a shield from discovery and trial in these cases. Across the five districts in my study, just thirty-eight (3.9%) of the 979 cases in which qualified immunity could be raised were dismissed on qualified immunity grounds. And when one considers all the Section 1983 cases brought against law enforcement defendants—each of which could expose law enforcement officials to burdens associated with discovery and trial—just seven (0.6%) were dismissed at the motion to dismiss stage and thirty-one (2.6%) were dismissed at summary judgment on qualified immunity grounds. My findings enrich our understanding of qualified immunity’s role in constitutional litigation, belie expectations about the policy interests served by qualified immunity, and show that qualified immunity doctrine should be modified to reflect its actual role in constitutional litigation.